Objective: To evaluate p53 protein expression in the endometrial polyp and compare with adenocarcinoma and atrophic endometrium of postmenopausal women. Materials and Methods: Ninety-eight postmenopausal women were included in this study and divided into three groups related to histopathologic diagnosis: Group A - endometrial adenocarcinoma (n = 40), Group B - endometrial polyp (n = 38), and Group C - endometrial atrophy (n = 20). The length of this study was from 1990 to 2004. The endometrial samples were collected from hysteroscopic biopsy or surgery then processed for histopathologic routine. One thousand cells of each histological section were evaluated for immunohistochemical analysis using p53 antibodies. The ANOVA test was performed for the statistical analysis. Results: The expression of p53 in adenocarcinoma samples was the highest. The expression of polyp was positive when associated to hyperplasia without atypia. All samples of atrophic endometrial were negative. Conclusions: The present data suggested that presence of hyperplasia in the endometrial polyp is factor to increase the expression of p53.